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The radioanalytical procedure for plutonium and americium has been described elsewhere (7). Cores 53 (1968) and 84.01377 (1984) were selected for the sequential leaching experements. This choice was made on the basis fo their similar 239+240 Pu activities (850 mBq g -1 ) in the surface (0-3 cm) sections. The samples analyzed in this work had a dry weight of 1 g and it has been shown that there is no relation between frequency of hot samples and sample size (4). The chemical partitioning studies of plutonium and americium were performed by sequential leaching. The fractions separated and determined were: Fraction 1: Exchangeable (1M CH3COONH4, 20 ml, 2h shaking) Fraction 2: Bound to carbonates (1M CH3COOH, 20 ml, 4 h shaking) Fraction 3: Bound to Fe/Mn oxides (0.1 M NH2OH,HC1 in 25% CH3COOH, 20 ml, overnight shaking) Fraction 4: Bound to organic matter - sulfides (H202 pH=2, 10 ml, 85°C, 6h shaking + 1M CH3COONH4, 15 ml, lh shaking) Fraction 5: Residual (conc. HNO3, HC104, HF) The sequential leaching experiment was done twice on each sample from 1984 and five times on the sample from 1968. The activities were corrected to the date of collection. In this context for the build up of 241 Am during sample storage, we used a 241pu/239+240 Pu activity ratio of 3.3 + 0.4 previously determined in 1968 (4). RESULTS AND DISCUSSION There are a great variety of chemical techniques which have been designed to establish the distribution of non-residual elements among the components of a sediment (8). The suitability, relative advantages and inconveniences of these methods have been reviewed at the International Laboratory of Marine Radioactivity in Monaco, and a standard method has been adopted after experimentation to check reproducibility. The method used in this work has been used previously to study transuranic geochemical partitioning in deep-sea and near-shore sediments (9-10). In order to reduce the effect on trace metal or transuranic concentrations which result from grain size difference, it is common practice to exclude the coarser sediment fraction by sieving. In most techniques, the fraction which has a grain size of < 60 pm is used for analysis. Little work has been carried out on the distribution of transuranics in sediments with regard to grain sizes characteristics, but for heavy metals at grain sizes>60 pm, presence of trace metal-rich heavy minerals or large-sized trace metal-poor minerals might affect the results. When performing. this work we encountered several difficulties such as the inhomegeneity of the samples and that the chemical partitioning of fallout plutonium and americium is not known. The fallout background is estimated to be 23 Bq m-2 (5) which is very small compared to the levels (30000 Bq m-2 ) found in this study. The influence on the results from such plutonium and americium is therefore not likely to be significant. we have not taken into consideration any alteration of chemical distribution during storage although this might have occured in practice
DOI link for The radioanalytical procedure for plutonium and americium has been described elsewhere (7). Cores 53 (1968) and 84.01377 (1984) were selected for the sequential leaching experements. This choice was made on the basis fo their similar 239+240 Pu activities (850 mBq g -1 ) in the surface (0-3 cm) sections. The samples analyzed in this work had a dry weight of 1 g and it has been shown that there is no relation between frequency of hot samples and sample size (4). The chemical partitioning studies of plutonium and americium were performed by sequential leaching. The fractions separated and determined were: Fraction 1: Exchangeable (1M CH3COONH4, 20 ml, 2h shaking) Fraction 2: Bound to carbonates (1M CH3COOH, 20 ml, 4 h shaking) Fraction 3: Bound to Fe/Mn oxides (0.1 M NH2OH,HC1 in 25% CH3COOH, 20 ml, overnight shaking) Fraction 4: Bound to organic matter - sulfides (H202 pH=2, 10 ml, 85°C, 6h shaking + 1M CH3COONH4, 15 ml, lh shaking) Fraction 5: Residual (conc. HNO3, HC104, HF) The sequential leaching experiment was done twice on each sample from 1984 and five times on the sample from 1968. The activities were corrected to the date of collection. In this context for the build up of 241 Am during sample storage, we used a 241pu/239+240 Pu activity ratio of 3.3 + 0.4 previously determined in 1968 (4). RESULTS AND DISCUSSION There are a great variety of chemical techniques which have been designed to establish the distribution of non-residual elements among the components of a sediment (8). The suitability, relative advantages and inconveniences of these methods have been reviewed at the International Laboratory of Marine Radioactivity in Monaco, and a standard method has been adopted after experimentation to check reproducibility. The method used in this work has been used previously to study transuranic geochemical partitioning in deep-sea and near-shore sediments (9-10). In order to reduce the effect on trace metal or transuranic concentrations which result from grain size difference, it is common practice to exclude the coarser sediment fraction by sieving. In most techniques, the fraction which has a grain size of < 60 pm is used for analysis. Little work has been carried out on the distribution of transuranics in sediments with regard to grain sizes characteristics, but for heavy metals at grain sizes>60 pm, presence of trace metal-rich heavy minerals or large-sized trace metal-poor minerals might affect the results. When performing. this work we encountered several difficulties such as the inhomegeneity of the samples and that the chemical partitioning of fallout plutonium and americium is not known. The fallout background is estimated to be 23 Bq m-2 (5) which is very small compared to the levels (30000 Bq m-2 ) found in this study. The influence on the results from such plutonium and americium is therefore not likely to be significant. we have not taken into consideration any alteration of chemical distribution during storage although this might have occured in practice
The radioanalytical procedure for plutonium and americium has been described elsewhere (7). Cores 53 (1968) and 84.01377 (1984) were selected for the sequential leaching experements. This choice was made on the basis fo their similar 239+240 Pu activities (850 mBq g -1 ) in the surface (0-3 cm) sections. The samples analyzed in this work had a dry weight of 1 g and it has been shown that there is no relation between frequency of hot samples and sample size (4). The chemical partitioning studies of plutonium and americium were performed by sequential leaching. The fractions separated and determined were: Fraction 1: Exchangeable (1M CH3COONH4, 20 ml, 2h shaking) Fraction 2: Bound to carbonates (1M CH3COOH, 20 ml, 4 h shaking) Fraction 3: Bound to Fe/Mn oxides (0.1 M NH2OH,HC1 in 25% CH3COOH, 20 ml, overnight shaking) Fraction 4: Bound to organic matter - sulfides (H202 pH=2, 10 ml, 85°C, 6h shaking + 1M CH3COONH4, 15 ml, lh shaking) Fraction 5: Residual (conc. HNO3, HC104, HF) The sequential leaching experiment was done twice on each sample from 1984 and five times on the sample from 1968. The activities were corrected to the date of collection. In this context for the build up of 241 Am during sample storage, we used a 241pu/239+240 Pu activity ratio of 3.3 + 0.4 previously determined in 1968 (4). RESULTS AND DISCUSSION There are a great variety of chemical techniques which have been designed to establish the distribution of non-residual elements among the components of a sediment (8). The suitability, relative advantages and inconveniences of these methods have been reviewed at the International Laboratory of Marine Radioactivity in Monaco, and a standard method has been adopted after experimentation to check reproducibility. The method used in this work has been used previously to study transuranic geochemical partitioning in deep-sea and near-shore sediments (9-10). In order to reduce the effect on trace metal or transuranic concentrations which result from grain size difference, it is common practice to exclude the coarser sediment fraction by sieving. In most techniques, the fraction which has a grain size of < 60 pm is used for analysis. Little work has been carried out on the distribution of transuranics in sediments with regard to grain sizes characteristics, but for heavy metals at grain sizes>60 pm, presence of trace metal-rich heavy minerals or large-sized trace metal-poor minerals might affect the results. When performing. this work we encountered several difficulties such as the inhomegeneity of the samples and that the chemical partitioning of fallout plutonium and americium is not known. The fallout background is estimated to be 23 Bq m-2 (5) which is very small compared to the levels (30000 Bq m-2 ) found in this study. The influence on the results from such plutonium and americium is therefore not likely to be significant. we have not taken into consideration any alteration of chemical distribution during storage although this might have occured in practice
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